。
She's not feeling well today.
Literal
She [topic-は] today [contrast-は] mood [subject-が] bad.
気分が悪い is famously dual-purpose: depending on context it means 'feels physically unwell, queasy' or 'is in a sour mood / disgusted.' On a moving train it leans nausea; in a heated argument it tilts toward emotional offense. The 気 ('spirit, energy, mood') in 気分 is the same kanji that anchors a huge cluster of feeling-words: 元気, 病気, 気持ち, 気にする, 気をつける. Compare 体調が悪い ('physically unwell'), which is unambiguous, and 機嫌が悪い ('in a bad mood'), which is unambiguously emotional.